<!DOCTYPE html>
<html>

<head>
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <style>
        body {
            margin: 0;
            min-width: 250px;
        }

        * {
            box-sizing: border-box;
        }

        ul {
            margin: 0;
            padding: 0;
        }

        ul li {
            cursor: pointer;
            position: relative;
            padding: 12px 8px 12px 40px;
            list-style-type: none;
            background: #eee;
            font-size: 18px;
            transition: 0.2s;

            /* make the list items unselectable */
            -webkit-user-select: none;
            -moz-user-select: none;
            -ms-user-select: none;
            user-select: none;
        }

        /* Set all odd list items to a different color (zebra-stripes) */
        ul li:nth-child(odd) {
            background: #f9f9f9;
        }

        /* Darker background-color on hover */
        ul li:hover {
            background: #ddd;
        }

        /* 当被点中的时候, 改变背景色, 改变字体色, 文字有中线 */
        ul li.checked {
            background: #888;
            color: #fff;
            text-decoration: line-through;
        }

        /* Add a "checked" mark when clicked on */
        /*  当被点中的时候, 展示那个小钩钩    */
        ul li.checked::before {
            content: '';
            position: absolute;
            border-color: #fff;
            border-style: solid;
            border-width: 0 2px 2px 0;
            top: 10px;
            left: 16px;
            transform: rotate(45deg);
            height: 15px;
            width: 7px;
        }

        /* Style the close button   小叉叉   */
        .close {
            position: absolute;
            right: 0;
            top: 0;
            padding: 12px 16px 12px 16px;
        }
        .close:hover {
            background-color: #f44336;
            color: white;
        }

        /* Style the header */
        .header {
            background-color: #f44336;
            padding: 30px 40px;
            color: white;
            text-align: center;
        }

        /* Clear floats after the header */
        .header:after {
            content: "";
            display: table;
            clear: both;
        }

        /* Style the input */
        input {
            margin: 0;
            border: none;
            border-radius: 0;
            width: 75%;
            padding: 10px;
            float: left;
            font-size: 16px;
        }

        /* Style the "Add" button */
        .addBtn {
            padding: 10px;
            width: 25%;
            background: #d9d9d9;
            color: #555;
            float: left;
            text-align: center;
            font-size: 16px;
            cursor: pointer;
            transition: 0.3s;
            border-radius: 0;
        }

        .addBtn:hover {
            background-color: #bbb;
        }
    </style>
</head>

<body>

    <div id="myDIV" class="header">
        <h2 style="margin:5px">My To Do List</h2>
        <input type="text" id="myInput" placeholder="Title...">
        <span onclick="newElement()" class="addBtn">Add</span>
    </div>

    <ul id="myUL">
        <li>Hit the gym</li>
        <li class="checked">Pay bills</li>
        <li>Meet George</li>
        <li>Read a book</li>
    </ul>




    <xmp style="font-size: 22px; font-weight: bolder;  margin-bottom: 66px;  color: black;  font-family: '微软雅黑';">
        
        必知必会

        字体库:
        <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/bootstrap-icons@1.8.1/font/bootstrap-icons.css">

        
        <div id="myDIV" class="header">
            <h2 style="margin:5px">My To Do List</h2>
            <input type="text" id="myInput" placeholder="Title...">
            <span onclick="newElement()" class="addBtn">Add</span>
        </div>
        
        <ul id="myUL">
            <li>Hit the gym</li>
            <li class="checked">Pay bills</li>
            <li>Meet George</li>
            <li>Buy eggs</li>
            <li>Read a book</li>
        </ul>
        
        /* 当被点中的时候, 改变背景色, 改变字体色, 文字有中线 */
        ul li.checked {
            background: #888;
            color: #fff;
            text-decoration: line-through;
        }

        /*  当被点中的时候, 展示那个小钩钩    */
        ul li.checked::before {
            content: '';
            position: absolute;
            border-color: #fff;
            border-style: solid;
            border-width: 0 2px 2px 0;
            top: 10px;
            left: 16px;
            transform: rotate(45deg);
            height: 15px;
            width: 7px;
        }

        for (i = 0; i < myNodelist.length; i++) {
            var span = document.createElement("SPAN");
            // 动态生成 小叉叉 按钮
            var txt = document.createTextNode("\u00D7");
            span.className = "close";
            span.appendChild(txt);
            myNodelist[i].appendChild(span);
        }
    </xmp>






</body>
<script>
    // Create a "close" button and append it to each list item
    var myNodelist = document.getElementsByTagName("LI");
    var close = document.getElementsByClassName("close");
    
    // 动态生成 小叉叉 按钮
    for (let i = 0; i < myNodelist.length; i++) {
        var span = document.createElement("SPAN");
        var txt = document.createTextNode("\u00D7");
        span.className = "close";
        span.appendChild(txt);
        myNodelist[i].appendChild(span);
    }



    //   点击 小叉叉 的时候, 隐藏父元素
    function cross() {
        for (let i = 0; i < close.length; i++) {
            close[i].onclick = function () {
                var div = this.parentElement;
                div.style.display = "none";
            }        
        }
    }

    cross();  // 初始化调用

    var list = document.querySelector('ul');
    list.addEventListener('click', function (eee) {
        if (eee.target.tagName === 'LI') {
            eee.target.classList.toggle('checked');
        }
    }, false);

    // Create a new list item when clicking on the "Add" button
    function newElement() {
        var li = document.createElement("li");
        var inputValue = document.getElementById("myInput").value;
        var t = document.createTextNode(inputValue);
        li.appendChild(t);
        if (inputValue === '') {
            alert("You must write something!");
        } else {
            document.getElementById("myUL").appendChild(li);
        }
        document.getElementById("myInput").value = "";

        var span = document.createElement("SPAN");
        var txt = document.createTextNode("\u00D7");
        span.className = "close";
        span.appendChild(txt);
        li.appendChild(span);

        cross();
    }
</script>
</html>
